P. A. Ronayne de Ferrer

Lactoferrin levels in term and preterm milk.

Objective: Even though there is no doubt that human milk is the best nourishment for the neonate, there is still controversy regarding its suitability for preterm infants. The aim of this study was to contribute to the knowledge of the anti-infective properties of preterm milk, measuring lactoferrin levels, which are a non-specific protective factor. Methods: Samples from 26 preterm and 20 term mothers (mean gestational age±standard deviation, 30.9±2.6 and 39.5±1.1 weeks, respectively) were collected during the first month post-partum. Milk samples were obtained by total expression of one breast between 10 a.m. and noon. An aliquot was kept at −20°C until analyzed by SDS-PAGE (sodium dodecyl sulfate-polyacrylarnide gel electrophoresis). Each sample was run in duplicate. Results: Lactoferrin levels (X±SD) in colostrum and mature milk varied from 575.0±218.2 mg/dL to 459.4±190.7 mg/dL in preterm samples and from 970.6±288.6 mg/dL to 292.0±167.4 mg/dL in term samples. No significant differences were observed between preterm and term groups, in spite of the trend observed in colostrum, where term milk tended to show higher levels than preterm milk. Decreasing values were observed in both groups along time (ANOVA, p<0.05). However, in the preterm group, lactoferrin levels seemed to maintain rather constant values from the eighth post-partum day onwards. Conclusions: The trend to higher levels of lactoferrin in preterm mature milk would allow maintenance of the protective effect of human milk in preterm infants in spite of the small volumes ingested by these neonates. These findings support the practice of feeding premature infants with their own mothers’ milk at a time when their immune systems have not completely developed.

Southern elephant seal, Mirounga leonina: composition of milk during lactation

An analysis of milk constituents during various stages of lactation in the southern elephant seal Mirounga leonina was carried out. Forty-six milk samples were taken from 30 females throughout lactation during 1985, 1987, 1990 and 1991 on Stranger Point, King George Island, South Shetland Islands. Total nitrogen (TN), non-protein nitrogen (NPN), sugar, fat, ash and water were measured, and from some of these data true protein and energy content were calculated. The results showed a high degree of variation in water and fat concentrations among samples at different stages of lactation. During the first 20 days the fat content of milk increased from about 12 to approximately 52%, while water content fell from 70 to 33%. The composition of milk changes rapidly during the first days post-partum. Protein, minerals and sugar appear to remain stable after the fourth day of lactation. Milk samples contain significant levels of sugars; thin layer chromatography indicates the presence of lactose and glucose together with other unidentified components. There is evidence of a striking change in composition of the milk in the later part of lactation; the progressive increase in the fat:water ratio is abruptly reversed just prior to weaning.

Southern elephant seal (Mirounga leonina) II. Studies of milk protein fractions by gel electrophoresis

Abstract Milk protein fractions during various stages of lactation in the southern elephant seal Mirounga leonina were analysed. Twelve milk samples were taken from ten females throughout the lactation period during 1990 and 1991 at Stranger Point, King George Island, South Shetland Islands. Milk samples were subjected to polyacrylamide gel electrophoresis (PAGE). Samples from different days of lactation gave similar qualitative electrophoretic patterns. True protein content was significantly higher (P<0.05) at the beginning of lactation, and then remained constant until weaning. Caseins and whey proteins each consisted of several protein entities (four and five distinct bands respectively). Casein constituted only about 30% of the protein nitrogen, the remaining 70% being derived from whey proteins. There was some variation in concentration of casein and whey proteins as a function of time (P<0.0.5).

Immunoglobulin A levels in southern elephant seal (Mirounga leonina) milk during the suckling period

Immunoglobulin A (IgA) levels in milk samples from southern elephant seals at King George Island, Antarctica are reported. IgA levels were determined throughout the suckling period (approximately 23 days). The IgA concentration in southern elephant seal milk was lower than in other mammals and, unlike most mammalian milk, was not high during early lactation. There was not a definite pattern in IgA levels, which fluctuated within narrow limits throughout the suckling period (mean +/- SD, 30.81 +/- 6.38 mg IgA/100 g milk). If IgG was present, its level was too low to be detected by the method used. This is the first evidence in Southern elephant seal of the possibility of transmission of passive immunity after birth involving secretion of IgA in the milk.

IMMUNOGLOBULIN M SERUM LEVELS IN FEMALES AND PUPS OF SOUTHERN ELEPHANT SEAL (MIROUNGA LEONINA) DURING THE SUCKLING PERIOD

This paper reports Immunoglobulin M (IgM) levels in serum samples from eight female-pup pairs of southern elephant seals (Mirounga leonina), at King George Island, Antarctica. IgM levels were determined on sera obtained from sequential sampling throughout the suckling period (approximately 23 days). The IgM concentration in southern elephant seal serum was measured by single radial immunodiffusion on agarose plates. Female IgM levels (123.5-613.0 mg/dL, n = 8) were significantly higher than pup levels (5.9-123.6 mg/dL, n = 8). Both groups showed an increasing trend throughout the entire suckling period, with significant differences in relation to stages of lactation. Pup IgM levels on the first day of life (mean +/- SD, 7.6 +/- 2.9 mg/dL, n = 3) suggest that endogenous synthesis takes place before birth.

Southern elephant seals: IgM concentration in milk of cows and serum of their pups

Abstract Serum and milk Immunoglobulin M (IgM) concentrations in 11 mother-pup pairs were measured in southern elephant seals (Mirounga leonina) throughout lactation during 2 breeding seasons at King George Island. Samples were obtained sequentially throughout the suckling period (approximately 23 days). The IgM concentration was measured by single radial immunodiffusion on agarose plates. Milk IgM concentrations showed significant differences throughout lactation, with the highest concentrations on the 1st day (x=989.7 mg/dL skimmed milk; SD=433.2) followed by a sharp fall during the next 3–6 days of the suckling period. The ratio of milk IgM/serum IgM concentrations from mothers ranged from 0.21 to 21.92, with highest values in the 1st day of lactation (x=8.25, SD=5.4) and a decrease in concentration as lactation progressed. This was due to the fact that, throughout lactation, milk IgM concentrations fell while serum IgM values showed an increasing trend. Pups showed the lowest serum IgM values in the 1st day of the suckling period (x=13.0 mg/dL, SD=4.3) with an increasing trend as lactation progressed. Despite the high IgM concentrations of milk at day 1 of lactation, by 1 week of age pups had serum IgM concentrations only slightly greater than at birth. This suggests that much of this Ig was newly formed and little or no milk IgM was absorbed during the 1st week. Possibly, the function of ingested IgM is to provide local immunity in the pups gut, during the first few days of postnatal life.